This invention relates to compositions and methods useful in the production of transgenic plants. In particular, the invention relates to Group 2 (Gp2) plant promoter sequences and to expression cassettes containing Gp2 plant promoter sequences. The invention also relates to vectors and transgenic plants containing Gp2 plant promoter sequences that are operably linked to heterologous DNA sequences. In addition, the invention relates to methods of producing transgenic plants by using vectors containing Gp2 promoter sequences.
Isolated plant promoters are useful in the genetic engineering of plants to produce transgenic plants with desired phenotypic characteristics. In order to produce such transgenic plants, an isolated plant promoter is inserted into a vector and operably linked to a heterologous DNA sequence. Plant cells can then be transformed in a variety of ways by DNA constructs containing an isolated plant promoter fused to heterologous DNA sequences. The result of this transformation is that the plant promoter operably linked to the heterologous DNA is inserted into the genome of the transformed plant cell. Furthermore, the regulation of the heterologous DNA in the transformed plant cell can be controlled by the expression of the promoter.
There are a variety of different approaches for producing a desired phenotype in a transgenic plant, depending on the nature of the heterologous sequences coupled to the isolated plant promoter. For example, expression of a novel gene that is not normally expressed in plant or in a particular tissue of a plant may confer a phenotypic change. Alternatively, the expression of a sense or an antisense construct introduced into transgenic plants can cause the inhibition of expression of endogenous plant genes. This inhibition of expression can, in turn, produce the desired phenotypic change.
There is a need for a variety of different promoters to be used in the genetic engineering of plants. These promoters are of several types. Constitutive promoters are one such commonly used type of promoter. Constitutive promoters are those which are capable of expressing operably linked DNA sequences in all tissues of a plant throughout normal development. In contrast to constitutive promoters, tissue-specific promoters are those promoters that are capable of selectively expressing heterologous DNA sequences in certain plant tissues. Tissue-specific promoters may also be inducible, e.g., by application of external inducing agents. Constitutive and tissue-specific promoters are both used in the genetic engineering of plants, and have value for many different potential applications in this field.
Constitutive plant promoters may be obtained by isolating the regulatory region of a plant gene that is constitutively expressed. In addition to promoters obtained from plant genes, there are also promoters of bacterial and viral origin which have been used to constitutively express novel sequences in plant tissues. Examples of such promoters from bacteria include the octopine synthase (ocs) promoter, the nopaline synthase (nos) promoter and others derived from native Ti plasmids (see Herrara-Estrella et al. (1983) Nature 303:209-213). The 35S and 19S RNA promoters of cauliflower mosaic virus are commonly used examples of viral promoters (see Odel et al. (1985) Nature 313:810-812).
In contrast to constitutive promoters, tissue-specific promoters are generally isolated from the promoter regions of plant genes that are selectively expressed in a specific plant tissue. These promoters can be fused with a heterologous DNA sequence and used to transform a plant cell to create transgenic plants that selectively express the heterologous DNA in a specific tissue. For example, the promoter regions from the fruit-specific, ethylene regulated genes E4 and E8 and from the fruit-specific polygalacturonase gene have been used to direct fruit specific expression of a heterologous DNA sequence in transgenic tomato plants. (See Cordes et al., Plant Cell (1989) 1;1025-1034, Deikman and Fischer, EMBO J. (1988) 7;3315-3320 and Della Penna et al., Proc. Natl. Acad. Sci. USA (1986) 83:6420-6424.)
The discovery of both new constitutive promoters and new tissue-specific promoters is desired for the controlled expression of various nucleic acid sequences that are genetically engineered into transgenic plants. There are many valuable potential applications of genetic engineering of plants. A variety of plant promoters with different characteristics and which are effective in different species of plants is desirable in order to bring these potential applications into practice.